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Pharmacology · Fluoroquinolones

Ofloxacin !

A fluoroquinolone mostly used today as eye and ear drops. Its active half, levofloxacin, replaced it for systemic use.

Updated 2026-11-01

  • Class: Fluoroquinolones
  • Enzyme: Bacterial DNA gyrase and topoisomerase IV
  • ATC code: J01MA01
  • WHO Model List of Essential Medicines

The figure shows levofloxacin, the active S-isomer of ofloxacin, bound to DNA cut by topoisomerase IV of Streptococcus pneumoniae.

Target in 3D: Bacterial DNA gyrase and topoisomerase IV. PDB structure 3RAE (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Ofloxacin is a racemic mixture whose S-isomer (levofloxacin) carries most of the activity. It traps DNA gyrase and topoisomerase IV on cut DNA, causing lethal double-strand breaks. Applied to the eye or ear it reaches high local levels with little systemic exposure.

  1. Applied to the eye or ear (or taken by mouth)
  2. Binds gyrase or topoisomerase IV on cut DNA
  3. The DNA cannot be resealed
  4. Double-strand breaks kill the bacterium

Pharmacokinetics

Absorption
Eye and ear drops act locally; oral forms are well absorbed where available.

Indications

  • Bacterial conjunctivitis (eye drops) Conjunctivitis →
  • External ear infection (ear drops; WHO list as an equivalent of ciprofloxacin) Otitis externa →
  • Bacterial corneal ulcers (eye drops)

Adverse effects

Common

  • Brief burning or discomfort in the eye
  • Bitter taste after ear or eye drops
  • Itching or redness

Contraindications

  • Allergy to ofloxacin, other quinolones or the product's components

Key interactions

Antacids and minerals (oral form)
Reduce absorption.
Other eye products
Applied a few minutes apart.

What is monitored

  • Response of the eye or ear infection
  • Signs of allergy

Administration and safety

  • Eye drops are not for injection
  • The dropper tip does not touch the eye or ear, to avoid contamination
  • Eye and ear products are not interchangeable unless labelled for both

Nursing care

  • Teach correct instillation and hand washing
  • Teach to report swelling, rash or worsening pain
  • Advise against contact lenses during an eye infection

Pregnancy and breastfeeding

Little reaches the blood after drops; systemic quinolones are usually avoided in pregnancy when alternatives exist.

Test yourself

Think of the answer, then tap the question to see it.

What is the relation between ofloxacin and levofloxacin?

Levofloxacin is the active S-isomer of the racemic ofloxacin.

For which ear infection is ofloxacin used?

External otitis (ear drops).

What is the most frequent effect of ofloxacin eye drops?

Transient burning or discomfort in the eye.

Add to my cards (3)

← Back to the class: Fluoroquinolones

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - OFLOXACIN- ofloxacin ophthalmic solution (DailyMed (U.S. National Library of Medicine), 2026); Ofloxacin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025).

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Representative model, for educational purposes only.